Blood Urea Nitrogen (BUN) is a vital parameter in assessing kidney function and overall health. Elevated BUN levels can signify various underlying medical conditions and health issues. Lowering BUN levels is often necessary to improve kidney health and overall well-being. Doctors order a blood urea nitrogen (BUN) test to measure the amount of urea nitrogen in your blood. It helps them see how well your kidneys are working.
What is Blood Urea Nitrogen (BUN)?
Blood Urea Nitrogen, often abbreviated as BUN, is a crucial component of blood chemistry. It is used to assess the efficiency of kidney function, specifically the ability of the kidneys to filter and remove waste products from the bloodstream. BUN is primarily composed of urea, a waste product generated by the breakdown of proteins in the body.
In a healthy individual, the BUN levels typically fall within a specific range, reflecting the balanced functioning of the kidneys. Normal BUN levels will be a number that measures how much BUN is in your blood. The range considered normal is 7-20 milligrams per deciliter. (A milligram is a very tiny amount-with over 28,000 milligrams in an ounce, and a deciliter is equal to about 3.4 ounces). When BUN levels rise beyond this range, it is a cause for concern as it suggests potential kidney dysfunction or other underlying health issues.
BUN Normal Values by Age and Sex
Normal BUN ranges can vary based on age and sex:
| Male or Assigned Male at Birth | Female or Assigned Female at Birth | |
|---|---|---|
| Ages 1 to 17 | 7 to 20 mg/dL | 7 to 20 mg/dL |
| Ages 18 and older | 8 to 24 mg/dL | 6 to 21 mg/dL |
Causes of Elevated BUN Levels
Several factors can lead to elevated BUN levels:
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- Kidney Dysfunction: Impaired kidney function is the most common cause of elevated BUN levels. The kidneys may be unable to effectively filter and remove urea from the bloodstream, resulting in its accumulation.
- Dehydration: Dehydration reduces the volume of blood flowing through the kidneys. As a result, the concentration of urea in the blood increases, leading to elevated BUN levels.
- High-Protein Diet: Consuming an excessive amount of dietary protein can lead to elevated BUN levels.
- Gastrointestinal Bleeding: Gastrointestinal bleeding, whether from ulcers, gastritis, or other sources, can introduce blood into the digestive system.
- Heart Failure: In cases of congestive heart failure, the kidneys may not receive adequate blood flow.
- Burns
- Several medications, including steroids and antibiotics
- Pregnancy
- Stress
- An inability to pee due to a blockage in your urinary tract
- Heart attack
- Gastrointestinal bleeding (bleeding in your digestive tract, such as your stomach, intestines, or esophagus)
- Your age
Why Healthy BUN Levels Matter
Maintaining healthy BUN levels is essential for overall well-being. Elevated BUN levels can indicate underlying health issues, especially kidney dysfunction, which is a serious concern.
- Kidney Health: High BUN levels are often a sign of kidney problems. If you have been told you have chronic kidney disease (CKD), you may be familiar with the lab values BUN and creatinine.
- Cardiovascular Health: Kidney dysfunction and elevated BUN levels are closely associated with an increased risk of cardiovascular diseases.
- Fluid and Electrolyte Balance: Elevated BUN levels can disrupt the body’s fluid and electrolyte balance, leading to issues like edema (swelling) and electrolyte imbalances.
- Overall Well-Being: Chronic elevation of BUN can lead to a range of symptoms and complications, including fatigue, nausea, and cognitive impairment.
The Connection Between High Protein Intake and BUN
Urea nitrogen is a normal waste product created in your liver as it breaks down certain proteins found in your food. Urea nitrogen travels through the blood to your kidneys, which filter out all but a small amount. Urea nitrogen exits from your body when you pee. When your kidneys are healthy, they remove BUN, usually leaving only a small amount in your blood. When your kidneys are not healthy, they leave more BUN behind.
In people with CKD, eating a high protein diet can contribute to elevation of BUN and creatinine. This is because these lab markers are involved with protein intake and protein stores in the body. The damaged kidneys are unable to remove excess amounts from the blood. For these reasons, restricting protein intake to about 0.6-0.8 grams per kilogram of body weight can be an effective way to slow the progression of CKD in some individuals.
Although high-protein diets continue to be popular for weight loss and type 2 diabetes, evidence suggests that worsening renal function may occur in individuals with-and perhaps without-impaired kidney function. High dietary protein intake can cause intraglomerular hypertension, which may result in kidney hyperfiltration, glomerular injury, and proteinuria. It is possible that long-term high protein intake may lead to de novo CKD.
The revived popularity of low-carbohydrate, high-protein diets may be partly fueled by their promotion across social media as an effective means for rapid weight loss and better glycemic control. For patients with CKD or at risk of CKD, high intake of dietary protein, including animal protein, may have detrimental effects on kidney function and long-term kidney health. The estimated average requirement for protein intake is 0.6 g of protein per kilogram of ideal body weight per day, which corresponds to the amount of protein required to avoid negative nitrogen balance and to meet half of a population’s requirements. The recommended daily allowance for protein intake is 0.83 g/kg per day and is calculated to meet the requirements of 97%-98% of the population (two SD above the estimated average requirement).1 Although there is a lack of consensus regarding the formal definition of a high-protein diet, most definitions set a threshold between 1.2 and 2.0 g/kg per day. Within this range, protein consumption >1.5 g/kg per day is generally considered to be a high-protein diet.
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Data from the National Health and Nutrition Examination Survey (NHANES) show that the current average consumption of protein in the United States is estimated to be approximately 1.2-1.4 g/kg per day,2 which is higher than the recommended amount. Popular weight-loss diets encourage higher amounts of protein while restricting the amount of carbohydrates, based on the assumption that all carbohydrates are undesirable-an assumption that has been refuted in the literature.3 Although such diets vary, these weight-loss strategies typically recommend that 25%-35% of calories consumed should be from protein and <45% of calories should be from carbohydrates.
Strategies for Lowering BUN Levels
The strategies for lowering BUN levels depend on the underlying cause of the elevation. It’s essential to identify and address the specific factors contributing to high BUN levels.
- Hydration: Dehydration is a common cause of elevated BUN levels. Increasing fluid intake is one of the most straightforward ways to lower BUN levels. For men or those assigned male at birth, that means about 3 liters (13 cups) of fluid each day. Women and those assigned female at birth should take in about 9 cups of fluid a day. (If you already have serious kidney disease or are on dialysis, too much fluid can cause problems, so follow your doctor's recommendation.)
- Limit Protein Intake: If a high-protein diet is contributing to elevated BUN levels, consider reducing your protein intake. This can help lower BUN levels over time. To reduce your BUN levels, don't eat more than 20-30 grams of protein a day.
- Medication Review: If medications are suspected to be causing elevated BUN levels, consult with your healthcare provider.
- Manage Underlying Conditions: If an underlying medical condition, such as kidney disease or hypertension, is responsible for elevated BUN levels, managing that condition is crucial.
- Dietary Modifications: In cases of gastrointestinal bleeding, dietary modifications to prevent irritation or injury to the gastrointestinal tract may be necessary.
- Nutritional Supplements: Some dietary supplements, like omega-3 fatty acids and antioxidants, may support kidney health and help lower BUN levels.
- Regular Exercise: Regular physical activity can help improve overall health and potentially contribute to better kidney function.
It’s important to note that while these strategies can be effective, they should be implemented under the guidance of a healthcare professional.
Dietary Considerations for Managing BUN Levels
Diet plays a crucial role in managing and lowering BUN levels, particularly when dietary protein intake is a contributing factor.
- Protein Restriction: If a high-protein diet is raising your BUN levels, consider reducing your protein intake.
- High-Quality Protein: When consuming protein, opt for high-quality sources, such as lean meats, poultry, fish, and plant-based proteins like legumes and tofu.
- Limit Purine-Rich Foods: Purines are substances found in certain foods that can be converted to uric acid and subsequently affect kidney function.
- Phosphorus Control: If you have kidney disease, monitoring phosphorus intake is important. High phosphorus levels in the blood can contribute to elevated BUN.
- Sodium Restriction: Reducing sodium (salt) intake can help control blood pressure and improve kidney function.
- Potassium Management: If you have kidney disease, it’s essential to manage potassium intake. High potassium levels can be harmful.
- Fluid Intake: Maintain adequate fluid intake to prevent dehydration.
- Antioxidant-Rich Foods: Include foods high in antioxidants in your diet, such as berries, dark leafy greens, and other colorful fruits and vegetables. Eat healthy foods, such as: Pasta, oats, and rice, Fruits including bananas, berries, and apples, Leafy green and other vegetables, Avocados, nuts, and healthy fats.
It’s crucial to tailor your diet to your specific needs and medical history.
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Lifestyle Modifications to Support Healthy BUN Levels
In addition to dietary changes, certain lifestyle modifications can help lower BUN levels and promote overall health.
- Stay Active: Engage in regular physical activity, as it can improve overall health and support kidney function.
- Quit Smoking: If you smoke, consider quitting.
- Limit Alcohol Intake: Excessive alcohol consumption can be detrimental to kidney health.
- Stress Management: High stress levels can affect overall health and potentially raise BUN levels.
- Monitor Blood Pressure: Regularly monitor your blood pressure and take steps to manage it within a healthy range.
- Manage Diabetes: If you have diabetes, effective management of blood sugar levels is essential.
- Regular Checkups: Stay up to date with routine medical checkups and screenings.
- Weight Management: Maintaining a healthy weight is important for kidney health.
Medical Interventions for High BUN Levels
In some cases, medical interventions may be necessary to lower BUN levels, especially if there is an underlying medical condition contributing to the elevation. The treatment and management of high BUN levels depend on the underlying cause and severity of the condition. In cases of dehydration, the primary treatment is fluid replacement.
There's no magic pill for treating high BUN levels. Doctors try to find out what's harming your kidney function and treat that condition.
Understanding Kidney Function Tests: BUN, Creatinine, and GFR
Several tests are used to assess kidney function, with BUN being one of them. It's often used in conjunction with other tests to provide a more complete picture of kidney health.
- Creatinine Test: A creatinine test is another blood test that checks your kidney health. You'd get it because the BUN level by itself doesn’t always reveal much. Creatinine is a waste product from your muscles that's also filtered by your kidneys. Like BUN, high levels of creatinine could mean there's a lot of waste product that hasn’t been removed by the kidneys. When your BUN levels are compared to your creatinine levels, it gives a fuller picture of what’s happening with your kidneys. This is known as the BUN/creatinine ratio. The ideal ratio of BUN to creatinine falls between 10-to-1 and 20-to-1. Having a ratio above this range could mean you may not be getting enough blood flow to your kidneys and could have conditions such as congestive heart failure, dehydration, or gastrointestinal bleeding. A ratio below the normal range could mean liver disease or malnutrition.
- Glomerular Filtration Rate (GFR) Test: The GFR test measures how well your kidneys filter waste from your blood. It will tell your doctor how much kidney function you have. A very low number means kidney failure, which means you'll need dialysis (a treatment that helps your kidneys remove waste or fluids from your blood) or a kidney transplant. Glomerular Filtration Rate (GFR) is another lab value you may see. It is a measure of kidney function. GFR determines the rate at which your kidneys are filtering blood. The result is used to identify what stage of kidney failure you are experiencing. If you know your creatinine level, you can use DaVita’s online GFR calculator to calculate and track your GFR . When GFR levels fall below 15mL/minute, dialysis is needed.
Addressing Low BUN Levels
Low BUN levels are rare. It's more likely if you have a small body. It could also point to: Liver disease Malnutrition (when your diet doesn’t have enough nutrients or your body can’t absorb them well) Overhydration (having too much fluid) A low-protein diet A BUN test by itself can't diagnose these issues, so more tests may be needed.
Having a low BUN level is usually not serious. However, if you want to raise your levels, you should eat more protein and improve the health of your liver by drinking less alcohol and losing weight.
Risks of a Blood Urea Nitrogen Test
Blood tests draw a small amount of blood, and there are usually few or mild side effects. You may have pain, bruising, or slight bleeding at the site where the blood is drawn. Some people may even feel lightheaded or faint. It doesn't happen often, but the site could get infected.